Isolation Of Photo-fermentation Bacteria And Best Mode For Photo-hydrogen Production

Increasingly serious environmental pollution and energy shortage forced humansto seek new sources of energy. Hydrogen, as a kind of green energy, has attracted wideattention. Photo-fermentative hydrogen production is an ideal process, due to organicpollution reduction. But the process has yet to realize large-scale production, becauseof the low hydrogen yield. In this paper, a new photo-fermentation bacterium strainwas isolated and a new disk photo-fermentation bioreactor was designed to producehydrogen. The hydrogen production characteristics of bacteria and the key parametersin the running bioreactor were optimized. The optimal operation and control strategyof the reactor were established, which could provide the theory and the technicalguidance for the large-scale photo-fermentation hydrogen production.A photo-fermentation bacterium strain A7was isolated from the running reactor.According to their morphology, fatty acid, blast of the sequences of16SrDNA andanalysis of phylogenetic tree, we characterized it as a new species of theRhodopseudomonas palustrisand. Optimal culture and hydrogen production conditionsof strain A7were determined in batch experiment. Its optimal culture and hydrogenproduction is the initial pH7.0, the temperature35℃, the light intensity of150W/m2, inoculation of10%, inoculants age14h, sodium acetate60mmol/L, sodiumglutamate15mmol/L.A disk photo-fermentation was designed to overcome the low light conversionefficiency of the existing photo-fermentation bioreactor. In the continuous operation,the reactor reached a maximum hydrogen yield (2.68mol H2/mol acetate) andhydrogen production rate (17.9mL/L/h), under the optimum HRT of2d and feedingtime of4d.In the semi-continuous operation, the reactor reached a maximum hydrogenyield (3.22mol H2/mol acetate) and hydrogen production rate (30mL/L/h), under theoptimum the first feeding time of4d, interval feeding time of1d and the feedingamount of40%.The light conversion efficiency of this disk photo-bioreactor was calculated, itwas1.6%and1.9%in the continuous operation and semi-continuous operation. It ishigher than that of the previous reports about photo-bioreactor. The high light conversion efficiency of this bioreactor was depended on optimal light, agitationsystem and temperature control.The modes for hydrogen production are compared. It was resulted that the bestmode for hydrogen production is semi-continuous mode. The main reason isthat,compared with other modes, the semi-continuous hydrogen production process iseasy to maintain microorganism, the system stability is good and easy to control.